Conventionally, power conversion devices, such as an inverter, have been applied to electric motors, vacuum cleaners, air conditioners, welding machines, and the like. In such a power conversion device, switching arms each of which has a high-potential-side semiconductor switching element and a low-potential-side semiconductor switching element connected in series are used. To these semiconductor switching elements, voltage control type semiconductor switching elements, such as an IGBT and a power MOS, have been applied.
As a power conversion device, a device including a rectifier circuit for converting AC power to DC power, a brake circuit, and an inverter circuit for converting DC power to AC power and control circuits therefor has been proposed (see PTL 1).
Recently, intelligent power modules in each of which a rectifier circuit, a brake circuit, and an inverter circuit and control circuits therefor are arranged in a single package are formed.
When an intelligent power module is configured as described above, wiring in the intelligent power module tends to be lengthened and wiring inductance tends to increase.
For this reason, when, for example, an IGBT, as a semiconductor switching element used for a brake circuit and an inverter circuit, is brought from an on-state to an off-state, an overvoltage (surge voltage) generated from stored energy stored in wiring inductance is supplied to between the gate, serving as a control terminal, and the emitter, serving as a low-potential-side terminal, of the IGBT.
In order to prevent the surge voltage from becoming higher than the breakdown voltage of the IGBT, setting up a surge voltage suppression circuit has been proposed as disclosed in PTL 2.
The surge voltage suppression circuit has a configuration including two Zener diodes that are connected in inverse series, that is, the anodes of both Zener diodes being connected to each other. The surge voltage suppression circuit is connected between the gate and emitter of the IGBT in parallel.